The present invention is directed to a process for the warp sizing of textile yarns and to the improved weaving properties of the yarns thus obtained. In addition, the invention relates to a process for warp sizing utilizing a warp size composition characterized by having improved compatability with textile sizing lubricants which moreover facilitates improved lubricant removability during desizing.
As used in this invention "warp" is an inclusive term which refers to the lengthwise running yarns in a woven fabric. A warp sizing material is any substance which is applied to the warp yarns for the basic purpose of strengthening and protecting the yarns from abrasion, usually as a result of its adhesive, film forming action. Warp sizes provide stiffness and smoothness to fibers which facilitate decreased incidents of entanglement and breakage during the weaving operation while also providing abrasion resistance to the fibers to avoid breakage and injury during handling.
The warp sizing, or slashing as it is often called, of textile yarns consists in the impregnation of these yarns with a sizing solution or dispersion. This is followed by removal of the excess sizing by passage of the wet yarns through a set of squeeze rolls followed by drying.
Warp sizing is carried out on a slashing machine consisting of a creel which generally holds one or more section beams. These section beams usually contain from 200-500 yarn ends. The yarn ends from several of these section beams are brought together so as to form a sheet of yarn with about 1500-8000 ends. This sheet then enters the size box wherein it is guided through the sizing solution and through one or more sets of squeeze rolls, so as to remove the surplus size which then falls back into the size box. Drying is accomplished by passing the yarn through a heated chamber or over the surface of internally heated drying cylinders.
The dried yarn is then separated by means of horizontal split rods into sections corresponding to those of the original section beams. The yarn is then almost immediately recombined by being passed through a vertical comb and thereupon onto a take-up beam referred to as a loom beam. This loom beam holds the yarn until such time as it is used in the weaving process.
One of the primary functions of the herein disclosed sizing process is to aid in the reduction of loom abrasion. To do this, the sizing must exert a film forming action, with the resultant film having the ability to resist the abrasive action of the various machine parts that come in contact with the yarns as well as the rubbing together of the individual yarns themselves.
Typical film-forming substances used as warp size materials have included starches, dextrins, glues, flours, gums, gelatin, cellulosics (i.e., carboxymethyl cellulose), polyvinyl alcohol, and polyacrylic acid. Many factors including the type and composition of fibers to be sized, construction, and count (weight per unit length) will determine which sizing materials or combination thereof should be employed.
Aqueous dispersions of starch and starch derivatives have been employed in the warp sizing of many natural, synthetic, or blended fibers. See, for example, the warp sizes of U.S. Pat. Nos. 2,946,705 (issued July 26, 1960 to H. Olsen) employing starch amine derivatives; 3,650,787 and 3,673,171 (issued Mar. 21, and June 27, 1972, respectively to L. Elizer) employing amphoteric and oxalkylated amphoteric starches; 3,719,664 (issued Mar. 6, 1973 to L. Hayes et al.) employing tertiary amine salts of starch half-acid esters; and 4,421,566 (issued Dec. 20, 1983 to M. Hasuly et al.) employing high amylose, cationic fluidity starch derivatives.
Lubricants are also conventionally employed in warp size compositions to improve weaving performance. The lubricants aid in reducing yarn-to-yarn and loom-to-yarn friction. Additionally they are noted to provide lubrication to loom parts during the later steps of the weaving process. Sizing compositions which evenly disperse the lubricants are particularly preferred as uniform lubricant distribution will help provide optimum weaving performance. The ability to improve loom efficiency (where 100%=no loom stops) by an amount of as little as 1 to 2% would be recognized in the field as a significant improvement.
Many varieties of fats, oils, and waxes obtained from various animal, vegetable, mineral, or synthetic sources have been advantageously used for such lubrication in typical amounts ranging from about 0.5 to 10%, based upon the weight of the film-forming substance. Mill waxes which generally comprise tallow and hydrogenated tallow glycerides are typically employed as size lubricants.
Although the presence of size is necessary to make a yarn weave satisfactorily, it is equally true that complete removal of the size is an essential prerequisite to successful finishing. Therefore, in most cases subsequent to weaving, the woven textile must be desized in order to avoid interference of the size with finishing processes such as, for example, bleaching, dyeing, printing, and water repellancy treatment. Depending on the size composition employed, desizing is accomplished by one or more steps including: enzymatic or oxidative degradation, high temperature washing, steaming, caustic scouring, and solvent or surfactant treatment.
Although the film-forming portion of the size composition will normally be completely removed by the above methods, removability of the lubricant is significantly more difficult, often requiring expensive and time consuming removal techniques. It has been estimated that only approximatey 25-30% of conventional size waxes on fabric are saponified or converted to water-soluble materials which are then removable. The remainder is not totally soluble and thus ends up on the fabric in the form of resist spots which are especially noticable after dyeing as exhibited by uneven dye penetration. Therefore, while uniform distribution of lubricant will result in the best weaving performance, it is also important for the textile finisher, who even if unable to remove it all, can achieve a condition which may permit a more regular and even appearance after dyeing.
Due to the current use of high speed air jet looms (with fill yarn insertion rates of 400-650 per minute as compared to 170-240 per minute for conventional looms), greater amounts of lubricants are sometimes employed to combat increased yarn stress encountered during weaving. With these higher quantities, lubricant removal, always a major cause for concern, is now aggravated.
It is an object of the present invention to provide a warp sizing composition capable of forming a uniform film upon warp yarns to sufficiently strengthen and protect them to withstand loom abrasion during conventional and high speed weaving.
It is a further object to provide a warp sizing composition capable of facilitating a uniform dispersion of textile lubricant in quantities equal to or greater than amounts conventionally used on the warp yarns.
It is also an object to provide a warp size composition which facilitates more complete lubricant removal after weaving employing inexpensive, less time-consuming methods.